The streets of Beirut were virtually empty today as Lebanon began three days of national mourning following the assassination yesterday of the former prime minister Rafik Hariri.

Schools, banks and shops closed as a mark of respect for Mr Hariri and the 13 others who police now say died in the bomb blast. About 120 people were injured.

Soldiers were deployed today at some intersections to prevent any possible violence. The armed forces have been put on full alert and troops' leave has been cancelled. TV stations and radios played sombre music or readings from the Koran, as the country prepared for Mr Hariri's funeral tomorrow at a downtown Beirut mosque.

Troops clamped a cordon around the bomb site, on a cosmopolitan stretch of the Beirut seafront. Explosive experts combed rooftops and the street in search of evidence as to the type of bomb that was used. Security officials have not confirmed initial reports that the blast was a car bomb.

The dead included Mr Hariri and seven of his bodyguards, crushed and burned in their heavily armoured cars by the force of the blast, which police estimated at about 300 kilos (660 pounds) of TNT.

A former economy minister and member of parliament in Mr Hariri's faction, Bassel Fleihan, was among the severely wounded. He was flown to France yesterday for treatment.

Residents in buildings near the blast were yesterday sweeping up the debris on their balconies. At the HSBC bank, workers cleared glass shards and blinds, throwing them down to the street.

The bomb that hit Mr Hariri's motorcade was in the very downtown district he helped to rebuild. Tourists had returned in recent years to gather at sidewalk cafes under buildings rebuilt in warm yellow stone.

Mr Hariri, 60, had resigned as prime minister in October, having led the government for 10 of the 14 years since the end of the 1975-1990 civil war. A billionaire businessman who made his fortune in construction in Saudi Arabia, Mr Hariri was a symbol of Lebanon's rebirth. Under his leadership, European investment and tourists returned to the country.

He had the wealth and prominence to maintain a degree of independence from Syria, which stations about 15,000 troops in Lebanon and is the effective power broker. After leaving office, Mr Hariri moved toward the opposition that has long pushed for an end to Syrian interference in Lebanon.

There have been no credible claims of responsibility for the assassination. A previously unknown group, Support and Jihad in Syria and Lebanon, claimed in a video broadcast on al-Jazeera television that it had carried out the bombing, saying it was a suicide operation.

Security officials have not confirmed the blast was the work of a suicide bomber. Late yesterday, police raided the west Beirut home of Ahmed Abu Adas, the Palestinian who allegedly appeared in the video. He had fled, but police confiscated computers, tapes and documents, the interior ministry said.

One statement posted on an Islamic website claimed responsibility for the bombing, but another web statement denied Islamic militants were involved. The country's justice minister, Adnan Addoum, said claims of responsibility could be an attempt "to mislead the investigation".